In his spartan Capitol Hill office, Katsaros explains how Nokero, the affordable, durable, sun-fuelled light, can help 1.6 billion people worldwide without electricity and wean them from dangerous kerosene lamps. ''You know how much money we could save on kerosene?'' says James Marshall, a Liberian who will soon be distributing Nokero bulbs in his homeland, where there is no network for electrical distribution.

''We are so in need of light. Most people use candlelight or kerosene,'' says Marshall, whose company, Africana SunPower, hopes to introduce solar power to West Africa. ''This product takes us out of darkness. With light we can study, we can cook. It will change people's lives. And it's affordable.''

Already Nokero bulbs are trickling into 33 countries, where tens of millions live without electricity. Bought in bulk, the bulbs cost about $6 each. Retail, they cost about $15.

''We are running a very, very lean operation to keep retail costs low enough so the 1.2 billion people who live on $2 a day can afford the light,'' Katsaros says. ''So every penny matters.''

At the Chinese factory poised to make 600,000 to 1.2 million bulbs a month, the rainproof lights are made with impact-resistant plastic and special computer chips to prolong battery life. Four solar panels charge the light, and they should last five years, providing up to four hours of light on a single charge.

A quarter of the world still burns fuel for light. Those burning lamps emit about 190 million tonnes of carbon dioxide into the atmosphere every year, the equivalent of emissions from 30 million cars or 1.3 million barrels of oil a day, according to an April report for the United Nations Framework Convention on Climate Change. Kerosene burners spend 5 per cent of their yearly income on fuel that provides inefficient light while creating burn and fire risks and significant indoor air pollution.

''With a combination of new technologies and appropriate market-delivery solutions, this situation can be reversed to a profound degree,'' the UN report From Carbon to Light says.

Katsaros is sure his solar bulb can be part of the answer. The Nokero bulb was born in January as Katsaros, a Denver native and father of two, pondered his next invention.

His story includes dozens of new gizmos. At high school ski races, Katsaros sold tools for tuning skis. While studying mechanical engineering at Purdue University, he won awards for his strapped-to-the-ceiling bike-storage system. He developed the first risers for ski bindings, which lifted boots higher off the ski and increased carving leverage.

Westinghouse bought a track-lighting system he designed. He designed a fog-killing fan that fits in most goggles, called the Haber Eliminator.

He spent five years designing RevoPower, a motorised bike wheel that works on any bike and delivers 30 km/h speeds and 1.2 litres per hundred kilometres (240 miles per gallon).

Everything he's done, he says, has led to the bulb. ''Everything just clicked with this project,'' he says, noting the rarity of moving an idea into reality and actual production in a matter of months.

As soon as he saw the first moulds of the bulb coming out of the factory, Katsaros, 37, quit the legal firm where he worked as a patent agent and devoted himself full-time to Nokero.

His plan is to target countries such as India, Indonesia, Nigeria and Pakistan, where hundreds of millions rely on expensive, carbon-spewing gas lamps but the income is high enough to afford a $15 lamp. Demand is higher in places such as Ethiopia, but the population is too poor to afford the lamp, Katsaros says.

''This is not a charity,'' he says. ''We are using capitalism as a method to improve people's lives.''